pontoon trailers 101
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Stress on Pontoon Trailer Frames

Pontoon trailers are subject to stress that ordinary boat trailers are not. When you’re towing a pontoon boat you need to understand why pontoon trailers are different. Most boat trailers carry the weight of the boat down the center of the trailer. The photo below, on the left, shows a heavy duty trailer for a large heavy fiberglas boat. The strength of the frame is important but not critical, since the weight of the boat is over the axle. Pontoon trailers carry the weight of the pontoon boat on centers often 77” wide. 

Standard Boat Trailer
The weight is down the middle.
Pontoon Boat Trailer
The weight is on 77" centers.
Most pontoon trailers are made from rectangular (box frame) steel. Gauges vary from 11 to 13 with 11 gauge being stronger. Anything thinner than 12 should be suspect. Some national trailer builders use 2” x 6” steel for the side frames, but it’s often thinner gauge. It’s difficult to know what kind of steel you’re getting in a trailer. Sales people won’t know and some manufacturers use one size and gauge for the frame and another for bracing. All you have to do to know what you’re getting is look at the trailer frame and how it’s braced. The cross bracing connecting the side frames of the trailer is more important than the gauge of steel. The weight of a pontoon boat is carried on 72” or 77” centers, as shown in the photo on the right above. The side frames of pontoon trailers have a tendency to twist and flex if there aren’t enough cross braces to reinforce the side frame. You’ll feel this when towing. If you’re not going more than a few miles it will just give you unpleasant vibration in the tow vehicle. But you’ll have to deal with it at some point because welds will crack. Forget the size and gauge of the steel, just look at how the frame is braced.
Standard Pontoon Trailer Frame  Heavy Duty Pontoon Trailer Frame 
Compare the two pontoon trailers shown above. The one on the left is obviously for a smaller pontoon, but the trailer will still experience twisting and flexing. There is no bracing and in fact the only thing holding the two sides together is the axle and the back cross member. The trailer to the right is for a large pontoon, but look at the multiple brace points.  

How Pontoon Trailer Frames are Braced

The twisting of a load on 77”centers creates stress on pontoon trailers that ordinary trailers aren’t subject to.
pontoon trailer frame
Don't know the gauge of the steel? Ask how much the trailer weighs. Some 24' tandems weight as little as 750 lbs. Most will weight 1000 lbs plus.
Weight tells you the strength of the the steel

A trailer with a strong well braced frame. The tongue extends to the second cross member. It has two additional braces to reinforce the frame.  Usually found on 22’ and larger tandem trailers.  
pontoon boat trailer bracing
pontoon trailer bracing examples
The photos above illustrate how the front of some brands of pontoon trailers are braced (or not braced). Because few companies use extra bracing you might conclude that it’s not necessary. To find out stand on the front of any of these trailers (behind the winch stand) and jump up and down. Brace yourself on the winch stand because the frame will flex and the trailer will bounce. You will be amazed at the amount of flex. You’ll feel that flexing when towing.
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